#/usr/bin/python

# imports of modules
import ConfigParser
import optparse
import os
import re
import random
import string
import subprocess
import sys

# defining some constants
AUTHZ_PATH = "authz"
HTPWD_PATH = "htpasswd"
SVN_DIR_CREATOR = "svn-dir-creator"
SVN_BASE = "cpi:/"

ADMINS     = "administrators"
REGULAR    = "users"
RESTRICTED = "restricted"
ALUMNI     = "alumni"

READ_ACL   = "r"
WRITE_ACL = "rw"

re_separators = re.compile("[\t ,;]+")

# helper functions
def group_users(users):
    """ uses the list of users to group them by their group name """
    groups = dict()
    for user in users.values():
        if user.group not in groups:
            groups[user.group] = []
        groups[user.group].append(user.name)
    return groups

def set_new_password(name, length=10):
    """ sets a new password for a username """
    characters = string.ascii_letters + string.digits
    password = "".join(random.choice(characters) for i in range(length))
    subprocess.check_call(["htpasswd", "-b", HTPWD_PATH, name, password])
    return password

def delete_password(name, length=10):
    """ deletes a password for a username """
    # if the user was not added to the password db, the removal will show
    # an error message that is confusing to the user - at least it confused me
    # so redirect this to /dev/null
    with open(os.devnull, 'wb') as devnull:
        subprocess.check_call(["htpasswd", "-D", HTPWD_PATH, name], stderr=devnull)
    


# class definitions
class User(object):
    """ Collect the username, group and access control lists """
    
    def __init__(self, name, group):
        """ initialization of the class """
        self.name = name
        self.group = group
        self.write_acl = []
        self.read_acl = []
    
    def __str__(self):
        """ return a string representation """
        return self.name
    
    def __repr__(self):
        """ return a string representation of the object """
        return "<User '%s@%s'>" % (self.name, self.group)


class AuthzConfigParser(ConfigParser.ConfigParser, object):
    """ custom functions for parsing the "authz" file as used at cpi """

    def __init__(self):
        """ initialization of the class """
        self.users = None
        super(AuthzConfigParser, self).__init__()
    
    def optionxform(self, value):
        """ reset the method to use cases ensitive names """
        return str(value)
    
    def extract_users(self):
        """ extract user information from config """
        users = dict()
        # first we go through the groups, as found in the groups section of the
        # authz file
        for group, userlist in self.items("groups"):
            for username in re_separators.split(userlist):
                if username in users:
                    raise Exception("Found duplicate entry for user " + username)
                user = User(username, group)
                users[username] = user
        # second we scan each section that is related to an svn folder (it 
        # starts with the svn base) for read and write access user entries
        for section in self.sections():
            if section.startswith(SVN_BASE):
                belongs_to = section.lstrip(SVN_BASE)
                for (option, value) in self.items(section):
                    if option in users:
                        if value.lower() == WRITE_ACL:
                            users[option].write_acl.append(belongs_to)
                        elif value.lower() == READ_ACL:
                            users[option].read_acl.append(belongs_to)
        # return the userlist
        return users

    def get_folder_info(self, name):
        """ returns read and write access info of an svn folder """
        if not name.startswith(SVN_BASE):
            name = SVN_BASE + name
        if not self.has_section(name):
            return None
        info = { WRITE_ACL: [], READ_ACL: [] }
        for (option, value) in self.items(name):
            if value in (WRITE_ACL, READ_ACL):
                info[value].append(option)
        return info
    
    def move_user_to_alumni(self, user):
        """ moves a user to the alumni group and removes every access rights """
        for access_to in user.write_acl:
            folder = SVN_BASE + access_to
            self.remove_option(folder, user.name)
        for access_to in user.read_acl:
            folder = SVN_BASE + access_to
            self.remove_option(folder, user.name)
        user.write_acl = []
        user.read_acl = []
        user.group = ALUMNI
        delete_password(user.name)
    
    def update_user_groups(self, users):
        """ updates the config settings of the groups section """
        groups = group_users(users)
        for group, userlist in groups.items():
            self.set("groups", group, ", ".join(sorted(userlist)))

    def write_to_file(self):
        with open(AUTHZ_PATH, "w") as filehandle:
            self.write(filehandle)

    def write(self, fp):
        """Write an .ini-format representation of the configuration state.
        
        this is adapted from the original library file. changes:
            - no default section
            - group-section at top
            - rest of section sorted by name
        """
        sorted_keys = sorted(self._sections.keys())
        sorting = ["groups"]
        sorting.extend([k for k in sorted_keys if k <> "groups"])
        for section in sorting:
            fp.write("[%s]\n" % section)
            for (key, value) in self._sections[section].items():
                if key == "__name__":
                    continue
                if (value is not None) or (self._optcre == self.OPTCRE):
                    key = " = ".join((key, str(value).replace('\n', '\n\t')))
                fp.write("%s\n" % (key))
            fp.write("\n")
        

if __name__ == "__main__":
    # create configparser instance
    config = AuthzConfigParser()
    # change option name transformation to case sensitive
    config.optionxform = str
    # read config file
    config.read(AUTHZ_PATH)
    users = config.extract_users()
    
    # command line interface:
    # no option: display info
    # -g         display users in a group
    # -a         add regular user
    # -r         add restricted user
    # -m         move to alumni
    # -p         reset user password 
    parser = optparse.OptionParser(
                usage="usage: %prog [option] name",
                description="shows and manipulates svn access rights",
                epilog="to grant a restricted user access to another folder, you have to carefully edit the authz file")
    parser.add_option("-g", "--groupinfo", action="store_const", dest="what", 
                      const="g", help="display users in a group")
    parser.add_option("-a", "--add", action="store_const", dest="what", 
                      const="a", help="add a regular user")
    parser.add_option("-r", "--restricted", action="store_const", dest="what", 
                      const="r", help="add a restricted user")
    parser.add_option("-m", "--move", action="store_const", dest="what", 
                      const="m", help="move a user to alumni")
    parser.add_option("-p", "--password", action="store_const", dest="what", 
                      const="p", help="reset a user password")
    options, args = parser.parse_args()
        
    if len(args)==0:
        # no arguments? then display all the users!
        groups = group_users(users)
        for name, usernames in groups.items():
            print "Users in group '%s':" % name
            for name in sorted(usernames):
                print "  " + name
        sys.exit()
        
    if len(args)>1:
        # more than one usename? not here, john boy
        sys.exit("please provide only one name")
    name = args[0]
    
    if options.what == "g":
        # show group information
        groups = group_users(users)
        if name not in groups:
            sys.exit("Group not found")
        print "Users in group '%s':" % name
        for usernamename in sorted(groups[name]):
            print "  " + usernamename
        sys.exit()
        
    if options.what in ("a", "r"):
        # add a user, restricted or regular
        if name in users:
            sys.exit("Username '%s' already in use" % name)
        group = RESTRICTED if options.what == "r" else REGULAR
        users[name] = User(name, group)
        config.update_user_groups(users)
        folder = SVN_BASE + name
        config.add_section(folder)
        config.set(folder, "@"+RESTRICTED, "")
        config.set(folder, name, WRITE_ACL)
        #subprocess.check_call(SVN_DIR_CREATOR + " " + name, shell=True)
        password = set_new_password(name)
        print "New password for user '%s': '%s'" % (name, password)
        config.write_to_file()
        sys.exit()

    # from here downwards we need already existent usernames
    if name not in users:
        sys.exit("User '%s' not found, use this without a name to get a list of users." % name)
    user = users[name]
        
    if options.what == "m":
        # move user to alumni
        groups = group_users(users)
        if user.group == ALUMNI:
            sys.exit("User '%s' is already in group '%s'" % (name, ALUMNI))
        if user.group == ADMINS:
            sys.exit("User '%s' is in group '%s', will not moved to '%s'" % (name, ADMINS, ALUMNI))
        config.move_user_to_alumni(user)
        config.update_user_groups(users)
        config.write_to_file()
        sys.exit()

    if options.what == "p":
        # reset a password
        password = set_new_password(name)
        print "New password for user '%s': '%s'" % (name, password)
        sys.exit()
        
    # no option, just a name:
    # print all the infos connected to a name
    print "User %s is in group '%s':" % (name, user.group)
    if user.group == ADMINS:
        print "  Write access is granted to all folders."
    elif user.write_acl:
        write_acl = [ SVN_BASE + username for username in user.write_acl ]
        print "  Write access is granted to folders '%s'. " % "', '".join(write_acl)
    else:
        print "  Write access is NOT granted to any folder"
    if user.group in (ADMINS, REGULAR):
        print "  Read access is granted to all folders."
    elif user.read_acl:
        read_acl = [ SVN_BASE + username for username in user.read_acl ]
        print "  Read access is granted to folders '%s'. " % "', '".join(read_acl)
    else:
        print "  Read access is NOT granted to any folder"
    info = config.get_folder_info(name)
    print "Labjornal %s%s:" % (SVN_BASE, name)
    write_acl = [ "@" + ADMINS ] + info[WRITE_ACL]
    print "  Write access granted to " + ", ".join(write_acl)
    read_acl = [ "@" + ADMINS, "@" + REGULAR ] + info[READ_ACL]
    print "  Read access granted to: " + ", ".join(read_acl)